See the original story in the Czech language.
On top of the Black Friday analysis, a new browser extension was born. Called Hlídač shopů in Czech, which can be translated as “Shop Watcher”, this allows any user to display product price trends on the three e-shops we monitor.
For example, the screenshot above shows how Alza changes the product price by several hundred Czech crowns every month. Savvy shoppers in the Czech Republic now have the opportunity to see where they are in the cycle and whether an advertised discount is real.
If you’re interested in our detailed analysis, you can read the Czech version here.
It really looks like the e-shops involved have made a big effort to eliminate the kind of price trickery that seemed to be occurring last year, although there is still room for improvement. On top of some minor anomalies when it comes to price fluctuations, of particular concern is that some shops were using different pages for the same product, with different prices for the page linked from the Black Friday promotion.
Another positive result — from the consumer point of view — from the publication of our original Czech-language analysis of Black Friday 2018 was that Mall.cz reacted swiftly to correct some errors. The day after our blog post, the website fixed a number of product recommended retail prices that we had highlighted as showing an exaggerated discount.
For this year’s analysis, we cleaned out all of last year’s data from our crawler and started to gather daily data, collecting product information directly from the product list based on category so as not to overburden the e-shop servers by visiting every product page. During the Black Friday promotion, we ran separate crawlers that ran four times per day.
At the end of Black Friday, we brought the dataset to Data Festak, where we put together an amazing team that programmed browser extensions through the night and began importing the data into Keboola. It ultimately took a few extra nights, but we are currently running the system using the following services:
Every day, Apify crawlers download the prices of all products on the three e-shops and import the data into Keboola. After data cleanup and transformation, it goes to Tableau, and at the same time to Elastic, from where the data is loaded by the Chrome and Firefox extensions.
We would like to thank Bizztreat for organizing Data Festak, our hackers from Apify and above all the team from Keboola and TopMonks, who helped on the analysis and are constantly working on improving the browser extensions.
As always, please let us know by contacting firstname.lastname@example.org if you have any feedback or suggestions!